Hydroxybenzoic acids and .alpha.-hydroxycarboxylic acids (known as "AHAs") have been used to treat skin conditions for over several decades. For example, .alpha.-hydroxycarboxylic acids have been used to treat ichthyosis, hyperkeratoses, dandruff and acne (see, U.S. Pat. Nos. 3,879,537 to Van Scott et al.; 3,920,835, 3,988,470, and 4,234,599 to Van Scott et al.; 3,984,566 to Van Scott et al.; and 4,105,782 to Yu et al.; respectively). .alpha.-Hydroxycarboxylic acids have also been used to treat dry skin (see, U.S. Pat. Nos. 4,105,783 to Yu et al.; 4,194,007 to Van Scott et al.; 4,197,316 to Yu et al.; 4,380,549 to Van Scott et al.; 4,363,815 to Yu et al. and 5,091,171 to Yu et al. .alpha.-Hydroxycarboxylic acids have also been used to enhance the antiinflammatory action of corticosteroids (see, U.S. Pat. No. 4,246,261 to Van Scott et al.). U.S. Pat. No. 5,254,343 to Parah et el. discloses the use of salts of .alpha.-hydroxyacids in conjunction with steroids to minimize cutaneous atrophy, a side-effect of steroid application to the skin. U.S. Pat. No. 4,542,129 to Orentreich teaches the use of a mixture of a keratolytic agent, such as a hydroxybenzoic acid or an .alpha.-hydroxycarboxylic acid, and dehydroepiandrosterone to treat dry skin while deterring acne formation.
Salicylic acid has also been used to treat conditions of the skin. International Publication No. WO 93/10756, published Jun. 10, 1993 to Blank teaches the use of salicylic acid to regulate wrinkles and/or atrophy in mammalian skin. U.S. Pat. No. 5,262,407 to Leveque et al. teaches the use of C.sub.1 -C.sub.18 alkanoyl 5-acylsalicylic acids to treat aging skin.
One of the drawbacks of using .alpha.-hydroxyacids or hydroxybenzoic acids, such as salicylic acid, for treating persons having skin ailments, however, is that at high concentrations, such acids are known to remove the outer layer of skin by chemically burning the skin off the patient. Such treatments are known in the art as "chemical peels." However, when improperly monitored, chemical peeling of the outer layer of skin using these acids can lead to inflammation, infection and scarring. In addition, .alpha.-hydroxyacids are known to cause skin irritation at certain lower levels in some individuals. Thus, there is a need for a composition capable of providing the skin-healing benefits of .alpha.-hydroxyacids or hydroxybenzoic acids, such as salicylic acid, while avoiding the drawbacks such as those described above.
Hydroxylated thioethers also been used to treat skin ailments. For example, U.S. Pat. No. 3,968,218 to Bouillon et al. discloses the use of hydroxylated amino thioethers for treating greasy skin.
Cysteamine derivatives have been used on the skin and scalp. FR 1,505,874 to Kalopissis discloses the use of S-benzylcysteamines for the treatment of seborrhea and acne. U.S. Pat. No. 4,089,942 to Bore et al. discloses deodorant compositions for body hygiene comprising S-benzylcysteamine or an organic salt thereof. U.S. Pat. No. 5,334,377 to Junino et al. discloses the use of cysteamine amides of aminoacids as reducing agents useful in a process for the permanent deformation of the hair. None of the above references suggest the use of sulfhydryl group-containing amides or disulfide group-containing bis-amides for treating or preventing abnormal skin conditions or diseases, and/or improving the texture or appearance of the skin. Moreover, none of the above references suggest the use of a compound which possesses the benefits of .alpha.-hydroxy or salicylic acids while avoiding their undesirable side effects. Thus, there is a need for cosmetic and pharmaceutical compositions with skin moisturizing and/or healing properties of .alpha.-hydroxycarboxylic and salicylic but without their deleterious effects.
German Patent Publication DE 1643487 discloses methods of synthesis useful for preparing various salts of S-substituted cysteamines.
PCT Publication No. WO 94/05302 to McCallum discloses the use of compositions comprising salicylic acid, elemental sulfur and cysteamine to treat "housewife dermatitis."
However, when compositions comprising more than one agent useful for treating skin are intended to be formulated, solvents or vehicles which successfully dissolve or suspend one of the necessary agents may be completely ineffective in dissolving or suspending the other(s), and vice versa. This can result in an excessive amount of time, energy and manpower required for determining the proper formulation solvents or vehicles. Further, chemical interactions among the one or more agents in a single formulation may render each agent inactive, or simply antagonize their activity. Thus, there remains a need for such a composition which can be efficiently formulated and/or which utilizes the advantages of one or more agents useful for treating skin.
As described below, the present invention provides novel compounds useful for treating or preventing abnormal skin conditions or diseases, and/or improving the texture or appearance of the skin with enhanced skin-healing properties. It further provides compounds which have the advantages of .alpha.-hydroxycarboxylic and salicylic acids without the above-mentioned biological disadvantages or formulation problems.
Additionally, the invention provides compositions comprising compounds having the advantages of .alpha.-hydroxycarboxylic and salicylic acids without the above-mentioned drawbacks.